Ring type antenna



Aug. 4, 1953 H. J. ROWL AND RING TYPE ANTENNA Filed April 11 1946INVENTOR., HOWARD J. ROWLAND ATTORNEY Patented Aug. 4, 1953 Howard J.Rowland, Brookline, by mesne assignments, ta the;

Mass assignor; United States. of

America as represented by the- Secretary of the Navy Application April11, 1946, Serial No. 6615205 5 Claims.

This invention relates to an antenna, and

more particularly to acompact multi-element' ring antenna havingintegral impedance matching stubs.

Ring type multi-eiement antennas are often employed when anomnidirectional radiation pattern is desiredin the plane of polarizationof the antenna. A conventional type employs a plurality of half-waveradiating elements arranged in arcs concentric with a coaxial feed line.When used at frequencies in which the length of the dipoleelementsbecomes appreciable, the physical dimensions become large andacomparatively bulky assembly results. Provision for effecting animpedance match of the radiating elements to the transmission line isnot included in conventional ring elements. Such matching is usuallyaccomplished by the application of" transformers. to the transmissionline.

It is an. object of this invention. to provide an improvedmul-ti-element ring antenna.

It isa further object of this invention to provide a. compactmulti-element ring antenna.

It is still another object of this invention to provide a compactmulti-element ring antenna having, integral means for-impedancematching. These and other objects will be more apparent uponconsideration of the following description together with theaccompanying drawings, Fig. 1 of which is a perspective view of anembodiment of the present invention. Fig. 2 is a partial plan view ofthe ring antenna of Fig. 1 showing the disposition of an adjustableprobe member.

Referring to the drawings, a metallic central collar 5, of properdiameter to fit snugly over the outer conductor of an associatedconventional transmission line, such as a coaxial line or circular waveguide (not shown), provides a rigid central support for three similardipole radiators, each occupying a 120 degree segment of a circle asshown. Spaced parallel dipole supporting arms 6 and 1 extend radiallyfrom collar 5 and support at their outer ends arcuate dipole elements 8and 9. Dipole element 8 extends at inner end 8' into the space betweenarms 6 and l and toward element 9. An aperture 4 is located in theextension 8', and is positioned midway between arms 6 and 1. Anadjustable probe I0 is threaded through the aperture 4 and extendsinwardly to a predetermined position within the transmission lineenclosed by collar 5. It has been found desirable that the separationbetween the radiating dipole elements in the plane of the elements beapproximately 180 2 electrical degrees for some applications, such aswhen a plurality of ring elements is employed'in an end flre lineararray. Because of the rather large dimensions of collar 5, as comparedwith the. wavelength usually used, the electrical length of arms-6 and 1will be somewhat less than 90- degrees, thereby presenting an inductivereactance at the operating frequency. 'Iheeffect of this reactance isneutralized by the addition of short parallel stubsl3 and I4,illustrated as integralextensions of the elements 8 and 9, which stubspresent a capacitive reactance at the operating frequency. Thus, theimpedance presented by the antenna to the transmission line iscontrolled by stubs f3 and I 4, eliminating the requirement of anadditional impedance matching transformer in the transmission line; Theplane of the placement of stubsl3 and M is unimportant. As shown in thedrawings, they are placed in a plane perpendicular to that of theantenna to provide acompact assembly.

As is well known, the current distribution along a dipole is suchthatthe free ends of the dipole contribute very little radiated energycompared with the central, or high current region; In order further toconserve space, the free ends of the dipole elements 8 and 9- have beenfolded to formloading stubs H- and IZ" respectively. Since some currentwill flow through stubs II and [2, it is desirable that they be placedin the same plane as the dipole elements 8 and 9 as illustrated toprevent cross-polarization effects.

The above described folded dipole unit comprises only one of threesimilar symmetrical assemblies, which as shown in the drawings arecombined and secured to collar 5 to form a complete antenna. It is notintended that the number of similar units shall be restricted to three,since any number of dipole elements lying in a common circle may beemployed if sufficient space is available. Since certain other changesmay be made in the above described article and different embodiments ofthe invention could be made without departing from the scope thereof, itis intended that all matter contained in the above description or shownin the accompanying drawings shall be interpreted as illustrative andnot in a limiting sense, and therefore that the invention is to belimited only by the prior art and the spirit of the appended claims.

What is claimed is:

1. An antenna structure comprising, a central collar, a plurality ofpairs of supporting arms extending radially outward from said centralcollar,

a plurality of arcuate dipole radiating elements arranged in a commoncircle in a common plane, each of said dipole elements being secured atone end to a separate one of said supporting arms, the unsecured ends ofsaid dipole elements extending radially inward toward said centralcollar, and a plurality of pairs of metallic stubs integrally joined tosaid dipole elements at the point of connection thereof with saidsupporting arms and extending perpendicularly in one direction from theplane of said dipole elements.

2. An integral antenna structure comprising, a central supportingcollar, a plurality of paired supporting arms extending radially outwardfrom said collar, a dipole element secured at one end to the extremityof each supporting arm with each pair of arms supporting a dipole, saiddipole elements being of arcuate form and arranged in a common circleconcentric with said collar, and a like plurality of paired metallicstubs integrally joined to said dipole elements at the point ofconnection thereof with said supporting arms, the stubs of each pairbeing parallel to each other and extending from said dipole.

3. An integral antenna structure comprising, a central supportingcollar, a plurality of paired supporting arms extending radially outwardfrom said collar, a dipole element secured at one end to the extremityof each supporting arm with each pair of arms supporting a dipole, saiddipole elements being of arcuate form and arranged in a common circle,the unsecured ends of said dipole elements extending radially inwardtoward said collar, and a like plurality of paired metallic stubsintegrally joined to said dipole elements at the point of connectionthereof with said supporting arms and extending parallel to the axis ofsaid collar in one direction from said dipoles.

4. An integral metallic antenna structure comprising, a centralsupporting collar adapted to be supported externally of a transmissionline, a plurality of paired supporting arms extending radially outwardfrom said collar, a dipole element connected at one end to the end ofeach supporting arm with each pair of arms supporting a dipole, saiddipole elements each being 01 arcuate form and arranged in a commoncircle concentric with said collar in a plane perpendicu- 4 lar to theaxis of said collar, the ends of said dipole elements not connected tosaid supporting arms being turned inwardly and extending a shortdistance radially toward said collar to provide capacitive couplingbetween adjacent dipoles, and a like plurality of paired metallic stubsintegrally joined to said dipole elements at the point of connectionthereof with said paired supporting arms and extending parallel to theaxis of said collar in one direction from the plane of said dipoleelements.

5. An integral metallic antenna structure comprising, a centralsupporting collar adapted to be supported externally of a transmissionline, a plurality of paired supporting arms extending radially outwardfrom said collar, a dipole element connected at one end to the end ofeach supporting arm with each pair of arms supporting a dipole, saiddipole elements each being of arcuate form and arranged in a commoncircle concentric with said collar in a plane perpendicular to the axisof said collar, an exciting probe connected at on end to the end of oneelement of each dipole and extending inwardly through said collar, theends of said dipole elements not connected to said supporting arms beingturned inwardly and extending a short distance radially toward saidcollar to provide capacitive coupling between adjacent dipoles, and alike plurality of aired metallic stubs integrally joined to said dipoleelements at the point of connection thereof with said paired supportingarms and extending parallel to the axis of said collar in one directionfrom the plane of said dipole elements.

HOWARD J. ROWLAND.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,283,897 Alford May 16, 1942 2,289,856 Alford July 14, 19422,324,462 Leeds July 13, 1943 2,402,635 Kandoian June 25, 1946 2,413,085Tiley Dec. 24, 1946 2,416,246 Wheeler Feb. 18, 1947 2,512,137 BuchwalterJune 20, 1950.,

